X-ray microanalysis, SEM

Scanning Electron Microscopy-Energy Dispersive X-Ray Microanalysis (SEM-EDX)... 

Identification of specific food components such as proteins and polysaccharides is possible by immuno-localization using gold-labeled antibodies (Figure 3). In conjunction with X-ray microanalysis, SEM is used to analyze salt crystals in cheeses, including... 

Subsequent investigation into what features might distinguish the femur from Burial 8 initially foeused on the mineral fraction of a selection of Snake Hill femora. Energy dispersive x-ray microanalysis (JEOL JSM-35C SEM equipped with a TN-5500 X-ray analyzer) demonstrated consistent calcium to... 

Williams et al. (2002) have reviewed the current state of AEM X-ray microanalysis, and they suggest ways in which the highest resolution of X-ray mapping may be achieved in the STEM with an EDS spectrometer. Because of their small collection angles and thin specimens, very small numbers of X-ray counts are generated, so the minimum detection limit is typically at best 0.1 wt%. This value is an order of magnitude worse than the 0.01 wt% figure for bulk-specimen in an SEM/EPMA. 

There is little doubt that cryotechniques, and particularly cryo-SEM, are now the dominant methods of specimen preparation for electron probe X-ray microanalysis when localization of soluble ions is required. In a previous review (5) these techniques were covered in considerable detail and this material is not reiterated here. Instead, protocols for the two major methods are provided and some recent developments and publications in this area are highlighted. 

Electron microscopy is an efficient microscopy technique that has been extensively used for the material characterization of artistic and archaeological objects, especially in combination with x-ray microanalysis [54], The use of electrons instead of light in these instruments is the basis of the higher resolution ( 9-0.2 nm) and has greater depth of held than LM. Thus, characterization of the finest topography of the surface objects is possible, and additional analytical information can be obtained. Different electron microscopes are currently used in art and art conservation studies scanning electron microscopes (SEM), Cryo-SEM... 

X-ray microanalysis techniques— in particular, electron probe x-ray microanalysis (EPXMA or EPMA) and SEM coupled with energy dispersive spectrometers (EDS, EDX) are, by far, one of the surface analysis techniques most extensively used in the field of art and art conservation, and they have actually become routine methods of analyzing art and archaeological objects and monitoring conservation treatments [34, 61, 63]. 

It is therefore frequently difficult to find punctual areas in the sample having a sufficient concentration of the desired analyte to be detected by the x-ray microanalysis system. Thus, identification and eventually quantitation of metals in dec-orative/protective layers of pictorial samples by SEM/EDX frequently require an accurate and often time-consuming scanning process. 

Analysis schemes developed for identifying clay minerals in the TEM based on EDS spectra (e.g., Murdoch et al.100) are inappropriate for colloidal samples dispersed on polycarbonate filters due to complications associated with the various sample-beam-substrate interactions that differ dramatically from that of ideal samples or standards with smooth polished surfaces.94 96 101 102 Correction procedures that account for the influence of particle size and morphology on x-ray spectra have been widely available for some time,101102 but these techniques have not been applied to the analysis of environmental particulates. To overcome the limitation of quantitative elemental analysis, some research groups have compared the x-ray spectra for sample colloids to the spectra for various minerals of similar size and composition under the same instrumental and sample preparation conditions to calibrate instrumental response.7 24 93 Noting the resolution problems associated with SEM analysis of submicron colloids, several research groups have chosen TEM as the primary discrete particle analysis technique,21 52 103 104 or have combined TEM analysis techniques, such as electron diffraction and x-ray microanalysis, to confirm conclusions drawn from SEM surveys.7,93 105... 

Figure 22 Si02 supported, MAO-activated zirconocene catalyst grains, Scanning Electron Microscopy (SEM) micrograph and element mapping by Energy-Dispersive X-ray Microanalysis.

Thanks to the linear relationship between the intensity of the characteristic X-ray radiation generated in the sample by electrons and the concentration of the given element, quantitative elemental analysis is also possible. X-ray microanalysis performed using SEM-EDX is, in principle, point analysis and is suitable for studying very small samples of solid materials that are stable in an electron beam. The X-ray fluorescence method, on the other hand, can be applied to the study of both solids and liquids. The signal reaching the detector always originates from a certain sample volume, and thus it is not point analysis. It is more sensitive than the SEM-EDX method. 

Using SEM and x-ray microanalysis. King and co-workers [25] followed the distribution of topically applied sulfur (10% precipitated sulfur in an aqueous cream base), lead (20% w/w, subacetate solution), zinc (calamine lotion), and fluorinated corticosteroids after topical application on the forearm of a human subject. It was found that the amount of sulfur, zinc, and lead were at higher concentrations in the deeper layers of the SC with increasing application time. The fluorinated corticosteroids were not detected within the skin. Information was not provided about the exact depth of penetration or the amount of each element found at different depths within the SC. It was, however, acknowledged that the combined SEM and x-ray microanalysis... 

Most SEMs today except those low end models are equipped with a spectrometer to perform X-ray microanalysis. This type of analysis, commonly known as energy-dispersive X-ray analysis DX or EDXRA), can reveal the elemental composition of a small spot (less than a square micron) in a membrane specimen. It can analyze a large number of elements except light elements such as carbon, nitrogen and oxygen. It is possible to carry out some analysis on some light elements with a light element detector. 

The particles were deposited on the slides by in5>actation, sedimentation and diffusion. Subsequently, the samples were analyzed by scanning electron microscopy (SEM). Information on morphology and size distribution was obtained from image analysis, while the elemental composition of particles was determined by electron probe X-ray microanalysis (EPXMA). 

Muir, M.D., Spicer, R.A., Grant, P.R. and Giddens, R., 1974. X-ray microanalysis in the SEM for the determination of elements in modern and fossil micro-organisms. In J.V. Sanders and D.J. Goodchild (Editors), Electron Microscopy 1974, Vol. II Biological, 8th International Congress on Electron Microscopy, Canberra, The Australian Academy of Science, Canberra, pp. 104—105. 

Figure 4.1 Structure of a scanning electron microscope (SEM). (Reproduced with kind permission of Springer Science and Business Media from J.I. Goldstein et al, Scanning Electron Microscopy and X-ray Microanalysis, 2nd ed., Plenum Press, New York. 1992 Springer Science.)...

Crushing ingots was carried out in a steel mortar in air. After each 3-5 min of crushing the powder was sieved through a sieve of 100 pm, and the coarser rest was crushed further. Ingot microstructure was studied by SEM technique in microscopes JSM-840 and Superprobe-733, the last microscope having an attachment for X-ray microanalysis. X-ray investigations were carried out in the X-ray unit DART-UM1 in CuKa emanation. 

Fracture mechanisms and microstructure as well as distribution of chemical elements along it were studied with scanning electron microscopy (SEM) and X-ray microanalysis (XRMA) using Superprobe-733, JEOL, Japan, after deep electrolytic etching with an etchant based on acetic acid. X-ray diffraction phase analysis was done with DRON diffractometer, Burevestnik, the Russian Federation. 

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